When an adhesive is applied to an adherend, and the adhesive includes a material having a coefficient of thermal expansion different from that of a material constituting the adherend, the two materials constituting the adhesive and the adherend thermally expand (or contract) in different degrees upon heating or cooling to cause a stress. The stress may disadvantageously cause peeling (separation) at the adhesive interface between the adhesive and the adherend. For example, such an adhesive is adopted to a recently studied technique of stacking two or more plies of a semiconductor device or wafer in a direction perpendicular to the substrate plane. According to this technique, two or more plies of a semiconductor device or a wafer are stacked and bonded with the adhesive to give a stack, and a through hole penetrating the stack is provided to form a through-silicon via. Thus, electrodes vertically connected to each other are provided with a higher degree of vertical integration. However, when a material constituting the adhesive has a coefficient of thermal expansion different from that of a material constituting the adherend semiconductor device, wafer, or through-silicon via, the two materials thermally expand (or contract) in different degrees upon heating or cooling to cause a stress. The stress may cause peeling (separation) at the adhesive interface between the adhesive and the adherend. In addition, the semiconductor device, wafer, and through-silicon via are thin-walled, fragile, and thereby liable to break when receiving external force applied as a result of heating or cooling.
According to a customary technique, an adhesive having a small difference in coefficient of thermal expansion from that of a material constituting the adherend has been employed to suppress peeling at the adhesive interface, which peeling is caused by the difference in coefficient of thermal expansion. This technique, however, should employ different adhesives from one adherend material to another and should thereby require adhesives of various types.
In contrast to this, an adhesive having sufficient flexibility, if developed, may avoid the need of employing different adhesives from one adherend material to another, because this adhesive can relax the stress which occurs between the adhesive and the adherend upon heating or cooling and which is caused by difference in thermal expansion. Patent Literature (PTL) 1 discloses a polymerizable resin composition including a polymerizable resin and a radically polymerizable monomer, in which the polymerizable resin is obtained by polymerization of monomer components containing an unsaturated monomer having an alicyclic epoxy group and/or an oxetane group in the molecule. The polymerizable resin composition, however, gives a cured material which is not sufficiently flexible and does not sufficiently relax the stress caused by difference in coefficient of thermal expansion between materials constituting the adhesive and the adherend.